Lead screw tapper



March 5, 1957 F. P. H. NACKENHORST LEAD SCREW TAPPER Filed Aug. 16, 1954INVENTOR.

fi ll E my my 8 l on s I I I 5 1 HQ 0 l I lllll I E I. I N I! ll [I.hfll h wi v N F h il 2 IQH=IQHQ W I. l .d m M uh x H ll. 1 I I 8 I 5 mmy l o w mm 2 1 L United States Patent i LEAD SCREW TAPPER Fred P.Nackenhorst, Drums, Pa., assignor to Oklahoma Steel Castings Co., Inc,New York, N. Y., a corporation of Delaware Application August 16, 1954,Serial No. 450,055

4 Claims. (Cl. 200-47) This invention relates generally to a lead screwtapper and in particular to an automatic reversing lead screw tapperwherein the depth of tap may be accurately and easily adjusted.

The tapper consists of a motor-operated lead screw which rotates in afixed lead screw nut so causing the screw to advance a tap which ismounted in a chuck attached to one end of the screw a predeterminedamount for each rotation of the screw. The screw has a fixed shoulderand a movable collar mounted thereon for axial movement which areadapted to engage a pivotally mounted lever when the tap reaches thelimit of its axial movement either towards or away from a work piece.Upon engagement of the lever by the shoulder or collar, the lever iscaused to rotate about its pivot and to contact one of two micro limitswitches, depending on whether the collar or the shoulder contacts thelever. Actuation of the micro limit switches causes the motor to reverseits direction of rotation and to withdraw or to advance the tap.

The tapper will be more easily understood by referring to the drawing inwhich is shown a side partial sectional view of a lead screw tapperconstructed according to my invention.

1 is a housing for the tapper unit and serves as a base for mounting theunit to a work table. 2 is a lead screw spindle mounted for rotation ina lead screw nut 3. Mounted on the end of lead screw 2 is a chuck 4which carries the tap 5. This chuck may be of the type known as a JacobsRubber Flex Chuck.

The lead screw 2 is rotated by a reversible electric motor 6 whose shaft7 is connected to a drive sleeve 8 by means of socket set screws 9 and19. This drive sleeve is connected to the lead screw 2 by means of adriving pin 11. The set screws 9 and 10 bear down on a key 12 which fitsin a keyway of the shaft 7 so that there can be no relative rotationbetween the shaft and the driving sleeve. The driving sleeve 8 isslotted as at 13 so that the driving pin 11 may slide axially of themotor shaft as the screw 2 is rotated in nut 3. The complete couplingassembly is surrounded by a drive sleeve cover 14 so that the assemblyis kept comparatively dust-free. This cover can be made of a materialsuch as neoprene so that it may be easily inserted over the drivingsleeve.

Mounted on the lead screw 2 is a collar 15 which can be moved axially ofthe screw in order to adjust for the depth of tap. This collar can beheld in place by a set screw 16 after it has been positioned. Also onlead screw 2 is a fixed shoulder 17 which is of the same radial width asthe collar 15. Both collar 15 and shoulder 17 are adapted to contactbearing 18 which is on one end of lever 19.

Lever 19 is made to pivot about a point 20 when it contacts eithercollar 15 or shoulder 17. Moving the lever about its pivot point 20causes it to contact either micro limit switch 21 or micro limit switch22, depending on which way the lever is rotated. Springs 23 and 24 are 42,784,267 C Pate'ntedMar. s, 1957 attached at the end of the lever awayfrom bearing 18 in order that the lever may be held in a neutralposition (one in which it does not contact a limit switch) whenever thebearing 18 is not in engagement with either shoulder 17 or collar 15.The micro-lirnit switches are of the common variety and are such thatthe slightest engagement of the lever with points 25 and 26 actuates theswitches. The switches in this form of the invention are so wired thatthey will cause complete reversal of rotation of the motor 6 when theyare actuated by the lever 19.

The lead screw nut 3 is retained at its inner end by bearing 27 whichserves as a bearing for the lead screw. This bearing is held in place bya retaining ring 28. Lead screw nut 3 is held in place on its outer endby from hear ing 29 which is held in place by a retaining nut 30. A feltseal 31 is fitted in a groove of retaining nut 30 so that the systemwill be oil-tight. The housing 1, bearings 27 and 29, and the lead screwnut are all keyed so as to receive a key 32 which prevents relativerotation among the parts. Oil cups 33 and 34 are provided so that thesystem may be readily lubricated.

The electric motor 6 has attached at the end opposite from the leadscrew tapper a Stearns magnetic brake 35. This brake stops rotation ofthe electric motor when actuated by the switches 21 and 22 and so allowsfor substantially instantaneous reversal of direction of rotation of thelead screw.

In operation the collar 15 is positioned so that the distance between itand the shoulder 17 is equal to the exact amount of depth of tap desiredin the work piece. The machine is then turned on which causes the leadscrew to rotate in one direction. Assuming that the lead screw begins torotate in a direction so that it advances towards the work piece, it isseen that the screw will continue to advance until the collar 15contacts bearing 18 of the lever 19. At this point the lever 19 willrotate about point 20 until the lever contacts point 25 of switch 22. Atthat instant switch 22 will then reverse the rotation of motor 6,causing the lead screw to advance towards the left as seen in thedrawings until shoulder 17 contacts bearing 18. This will then actuateswitch 21 which will reverse rotation of the lead screw and so repeatthe cycle. It is to be understood that switches 22 and 23 could be setup so that insead of causing the motor 6 to reverse its rotation, theycould merely cause the motor to stop. This arrrangement would thennecessitate another switch for starting the motor.

It is obvious that taps of different pitch could be used by merely usinga different pitch on the lead screw and on the lead screw nut. It isseen from the drawings that by removing retaining nut 30 and raising theunit carrying the limit switches, that the complete lead screw and nutassembly can be easily removed and a new assembly inserted in place ofthe old.

It is a further advantage of my lead screw tapper that it is adapted formass production methods of manufacturing wherein extreme tolerances mustbe maintained. A series of such units could be set up in many differentpositions surrounding work pieces in order to tap as many holes in asmany positions as was desired.

1 claim:

1. A lead screw tapper having a housing, a motor, a tap-carrying leadscrew adapted to be rotated by said motor, a fixed lead screw nutengaging said lead screw, a fixed shoulder on said lead screw, anaxially adjustable collar slidably mounted on said lead screw, and apivoted lever adapted to be engaged by said shoulder and said collarupon the extreme limits of axial travel of said lead screw; said leverupon engagement with said shoulder and collar being made to rotate aboutits pivot point to actuate a pair of micro-limit switches.

2. A lead screw tapper according to claim 1, having in said screw nutand collar are adapted to fit into a bore in addition spring means forcentering-said lever in a neutral said housing as a unitary member."position when not in engagement with said collar and aid hould r,References Cited in the file of this patent ead screw tapper accor ing tla m' wherein 5 UNITED STATES PATENTS said spring means comprises twosprings connected'to the I q end of the lever opposite the end of saidlever adapted to 496372 Ward "."T May 1893 engage said shoulder and saidcollar. EQBEIGN PATENTS lead screw m: fcp d ps t dai 1 rg y seo,osoGreat Britain Apr. 12, 194p

